1. Field of the Invention
The present invention relates to an image formation apparatus of an electrophotographic system, comprising an electrostatic latent image carrier such as a photosensitive drum, for use in a laser printer, a copying machine, etc.
2. Description of the Related Art
An image forming apparatus of an electrophotographic system, which comprises an electrostatic latent image carrier, for example, a photosensitive drum, has the structure in which a charge device, an exposure device, a development unit, a transfer changer device and a discharge device are arranged around the photosensitive drum.
In this image formation apparatus, the photosensitive surface of the photosensitive drum is charged uniformly by the charge device while rotating the drum.
The charged photosensitive surface of the drum is exposed to scanning light from an optical unit provided in the exposure device, thereby forming an electrostatic latent image on the surface. The electrostatic latent image is developed by toner applied thereon from the development unit so as to be visualized as a toner image.
The toner image is transferred on an image transfer sheet by the transfer charger device. The image transfer sheet to which the toner image has been transferred, is heated and pressed by a heat fixation device for fixation of the image.
Such an image formation apparatus is disclosed in, for example, Jap. Pat. Appln. KOKAI Publication No. 4-51257, or Jap. Pat. Appln. KOKAI Publication No. 3-249766.
According to Jap. Pat. Appln. KOKAI Publication No. 4-51257, the apparatus body 1 is divided into the upper body 1a and the lower body 1b, as shown in FIG. 9.
The upper body 1a has an image formation case 8 which further includes an optical writing device 2, a photosensitive drum 3, a charger device 4, a development device 5, a cleaning device 6 and a discharger device 7.
The lower body lb contains a transfer charger device 9, a fixation device 10 and a conveyer path 11. The lower body lb further includes a sheet feeding tray 13 detachably provided on the outer side of the conveying path 11, and in the tray, sheets 12 are stored.
The upper and lower bodies 1a and 1b of the apparatus body 1 are placed one on the other such that one end side can be opened while the other end side is hinged.
In the image formation apparatus having the above-described structure, the jamming of a sheet 12 on the conveyance path 11, the transfer charger device 9 or the fixation device 10 occurs in some cases. When it occurs, the upper and lower bodies 1a and 1b are opened, as shown in FIG. 10, so as to uncover the conveyance path 11, the transfer charger 9 and the fixation device 10, and the jammed paper is removed.
Jap. Pat. Appln. KOKAI Publication No. 3-249766 discloses an apparatus body 21 as shown in FIG. 11, in which a scanning optical system 22, a fixation device 23, a transfer charger roller 24, a paper-feeding cassette 25, etc are accommodated.
An image formation unit 29 comprising a photosensitive drum 26, a charger roller 27, a development device 28 and the like, may be set in the device body 21 by inserting from the upper surface thereof obliquely downward. The image formation unit 29 is set to the device body 21 such that the upper portion thereof is uncovered, and therefore it can be easily removed therefrom by pulling it upward, as shown in FIG. 12.
According to Jap. Pat. Appln. KOKAI Publication No. 4-51257, the apparatus body 1 has the structure in which the upper and lower bodies 1a and 1b can be opened at one side, and therefore a large-scale opening mechanism is necessary, which enlarges and complicates the apparatus.
In the case where the jamming of a sheet takes place at the fixation device, the upper body 1a must be opened, and a user must put his/her hand deep inside the apparatus to remove the jamming of the sheet. In practice, the upper body 1a serves to block the removal of the sheet, and therefore such an operation is difficult.
According to Jap. Pat. Appln. KOKAI Publication No. 3-249766, the apparatus body 21 has the structure in which the image formation unit 29 is inserted thereto obliquely downward, as shown in FIGS. 11 and 12. Therefore, the scanning optical system 22 accommodated in the upper body serves to cover the inside, and therefore it is not easy for the user to look inside. Thus removal of the jammed sheet is difficult. In the case where the size of the whole apparatus is decreased with the technique disclosed in Jap. Pat. Appln. KOKAI Publication No. 3-249766, the size of the image formation unit 29 is according reduced, thus making it difficult for the user to put his/her hand into the cavity in which the unit 29 is accommodated, after it is removed therefrom.